1. Field of the Invention
The invention disclosed and taught herein relates generally to fixed cutter or drag type bits for drilling subterranean formations and, more specifically, relates to drag bits or impregnation bits for drilling hard and/or abrasive rock formations, and especially for drilling such formations interbedded with soft and non-abrasive layers.
2. Description of the Related Art
In order to provide background information so that the invention may be completely understood and appreciated in its proper context, reference may be made to a number of prior U.S. patents as follows:
U.S. Pat. No. 6,510,906 to Richert et al., issued Jan. 28, 2003, discloses an “impregnated bit with PDC cutters in cone area.” In one embodiment, a drill bit employing a plurality of discrete, post-like diamond grit impregnated cutting structures extending upwardly from abrasive particulate-impregnated blades defining a plurality of fluid passages therebetween on the bit face is disclosed. In another embodiment, PDC cutters with faces oriented in the general direction of bit rotation are placed in the cone in a bit, which is relatively shallow, to promote enhanced drilling efficiency through softer, non-abrasive formations.
U.S. Pat. No. 6,843,333 to Richert et al., issued Jan. 18, 2005, discloses an “impregnated rotary drag bit.” In one embodiment, a drill bit employing a plurality of discrete, post-like abrasive, particulate-impregnated cutting structures extending upwardly from abrasive, particulate-impregnating blades defining a plurality of fluid passages therebetween on the bit face is disclosed. In another embodiment, additional cutting edges may be placed in the cone of the bit surrounding the centerline thereof.
U.S. Pat. No. 6,009,962 to Beaton, issued Jan. 4, 2000, discloses “impregnated type rotary drill bits.” In one embodiment, a rotary drill comprises a bit body having a leading surface formed at least in part from solid infiltrated matrix material, a major part of the leading surface being impregnated with abrasive particles of a diamond or other superhard material. There are also mounted a plurality of larger cutting elements having cutting edges formed of superhard material that project above the surface, the larger cutting elements being so spaced as to define a substantially continuous cutting profile, so that the cutting elements in combination sweep over the entire bottom of a hole being drilled by the bit, during each revolution.
The invention disclosed and taught herein is directed to an impregnation bit with improved cutting structure and blade geometry.